The transition metals, particularly cobalt (Co), nickel (Ni), titanium (Ti), zirconium (Zr) and hafnium (Hf), and their silicides recently have been investigated as candidates for ohmic contact or interconnection materials that can be used in ultralarge scale integrate (ULSI) circuits. These metals and their silicides exhibit desirable properties including low resistivity, thermal and chemical stability, and a high possibility of selective growth. Epitaxial silicides are particularly attractive due to their superior electrical conductivity for contact applications.
Hf3Si2 films have been recognized as one of the more promising constituent materials for metallization systems because of their low Schottky barrier height for silicon and the low contact resistivity of Hf3Si2, which typically is formed by the interfacial solid phase reaction of a hafnium/silicon system. However, growth of Hf3Si2 layers overlying silicon has proven difficult because hafnium can form a variety of other stoichiometric silicide phases in a hafnium/silicon system, including Hf2Si, Hf5S4, HfSi, and HfSi2. The epitaxial growth of Hf3Si2 on silicon also has proven challenging because silicon has a cubic structure, while Hf3Si2 has a tetragonal structure.
Accordingly, it is desirable to provide processes for fabricating semiconductor structures having high quality epitaxial Hf3Si2 layers. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.